1. Field of the Invention
The present invention relates to a method of manufacturing a nozzle plate, a nozzle plate, a liquid ejection head, and an image forming apparatus, and more particularly, to a method of manufacturing a nozzle plate, a nozzle plate, a liquid ejection head and an image forming apparatus, in which a liquid-repelling film is formed on the surface of a nozzle plate on the liquid droplet ejection side thereof, and a liquid-philic film is formed on the other parts of the nozzle plate.
2. Description of the Related Art
Print heads installed in an inkjet type of image forming apparatus include heads provided with a nozzle plate on a surface opposing the recording medium, in which liquid droplets (ink droplets) are ejected toward the recording medium from a plurality of nozzles formed in the nozzle plate.
A nozzle plate is known in the related art in which a liquid-repelling film is formed on the liquid droplet ejection surface of the nozzles plate, in order to stabilize the direction of flight of the liquid droplets ejected from the nozzles and to stabilize the meniscus of the ink in the nozzle, and a liquid-philic film is formed on the other parts of the nozzle plate (for example, the inner walls of the nozzles), in order to improve the ink supply performance and to facilitate control of the back pressure.
In the present specification, the term “liquid-philic” means “having a strong affinity for the liquid (e.g., the ink)”. For example, in the case where the liquid or the ink is an aqueous solution or water-based, the terms “liquid-philic” and “liquid-philicity” correspond to “hydrophilic” and “hydrophilicity”, respectively. On the other hand, in the case where the liquid or the ink is an oleaginous solution or oil-based, the terms “liquid-philic” and “liquid-philicity” correspond to “oleophilic” and “oleophilicity”.
For example, Japanese Patent Application Publication No. 9-267478 discloses a method of manufacturing a nozzle plate in which a water-repelling and oil-repelling film is formed over the entire surface of the nozzle plate, silicone rubber is bonded onto the water-repelling and oil-repelling film on the front surface of the nozzle plate, and the plate is exposed to oxygen plasma, whereby the water-repelling and oil-repelling film on the parts other than the front surface is removed thus making those parts hydrophilic and oleophilic.
Japanese Patent Application Publication No. 2002-187267 discloses a method of manufacturing a nozzle plate in which a liquid-repelling film is formed on the whole surface of a nozzle plate, whereupon the front surface of the nozzle plate is sealed with a resist, the liquid-repelling film that is not covered with the resist is removed, a liquid-philic film is formed on the surface where the liquid-repelling film has been removed, and finally, the resist is removed.
However, the oxygen plasma processing in Japanese Patent Application Publication No. 9-267478 does not produce sufficient liquid-philicity, and moreover, the produced liquid-philicity deteriorates with the passage of time. Furthermore, since the interface between the base material and the liquid-repelling film makes contact with the ink, then there may be erosion at the interface and corrosion of the base material.
On the other hand, in Japanese Patent Application Publication No. 2002-187267, since the whole surface of the nozzle plate is covered with the liquid-repelling film and the liquid-philic film, then the problems associated with Japanese Patent Application Publication No. 9-267478 do not occur. However, the manufacturing method requires steps for removing the liquid-repelling film and the resist, and the like, and this makes the manufacturing process more complicated. For example, if etching is performed to remove the liquid-repelling film, then it is difficult to achieve uniform reaction speed and churning of the solvent and the etching depth of the resist, between the nozzles, and this gives rise to ejection nonuniformity between the nozzles. Moreover, blasting and ashing, and the like, are also possible methods for removing the liquid-repelling film; however, it is difficult with these methods to uniformly remove the liquid-repelling film at all of the nozzles without damaging the base material. Further, it is also possible to form a liquid-repelling film that is readily removable, by adjusting the composition of the liquid-repelling film; however, the liquid-repelling film of this kind would have weak resistance to scratching and the action of chemicals, thus leading to deterioration in production specifications. Furthermore, in a method which uses mask processing with a resist, an interface between the liquid-repelling film and the liquid-philic film becomes present inside the nozzle, and the interface does not coincide with the meniscus position formed at the opening section of the nozzle, and hence it can lead to deterioration in the ink supply performance, as well as making the control of the back pressure more difficult.